JP2007208571A - Communication system, communication device, congestion control method used for them, and its program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication device which is capable of improving in throughput even while a loss rate is high without any special notification of information as to congestion from a network. <P>SOLUTION: A congestion decision unit 21 determines whether a current state of congestion is light or heavy from an ACK packet and contents stored in a session state storage unit, and transfers processing to a network state estimation unit 22 or a usual transfer unit 27 corresponding to decision results. The network state estimation unit 22 estimates the congestion state of a network from the ACK packet and the contents stored in the session state storage unit. A light/heavy congestion decision unit 23 determines whether a current state of congestion is light or heavy from the estimation results of the network state estimation unit 22, and transfers processing to a resending decision unit 24 or a heavy congestion resending unit 25. The resending decision unit 24 judges whether a segment that is not resent yet is contained in the segments that are requested to be resent from a recipient through ACK, and transfers processing to a light congestion resending unit 26 or a usual transfer unit 27 corresponding to the decision results. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a communication system, a communication apparatus, a congestion control method used therefor, and a program thereof, and more particularly to a protocol layer session control technique having a congestion control function in a communication system using packet switching.

  In packet switching, some protocols for establishing a session include flow control for controlling the speed on the sending side so as not to exceed the reception processing capacity on the receiving side, and the speed on the sending side so as not to cause network congestion on the way. There is one having both functions of congestion control for controlling the above (hereinafter, both functions are collectively referred to as rate control).

  In general, this rate control function is often implemented in the transport layer of an OSI (Open Systems Interconnection) reference model. As the rate control method, there is a window control type. The window control type is a method of adjusting the amount of staying in the network around 1 RTT (Round Trip Time). Currently, TCP widely used in the Internet is also a window control type transport layer protocol, and has a congestion control function.

  In TCP, congestion control is performed on the transmission side, and a response confirmation packet [ACK (ACKknowledgement) packet] from the reception side is used to change the state of congestion control to increase the packet transmission amount or detect packet loss. Reduce the amount of transmission and retransmit the packet. The amount of packets sent is determined by CWND (congestion window), which is the amount of packets that can be transmitted around 1 RTT, and the transmitting side receives data for CWND from the maximum value of the sequence number (ACK number) notified by the ACK packet. You can go to

  When the sequence number in the ACK packet from the receiving side is increasing, the transmitting side continues to increase CWND and continues to increase the packet transmission amount. The increase width of CWND varies depending on the relationship between CWND and SSTHRESH (slow start threshold). When CWND ≦ SSTHRESH (slow start state: Slow Start Phase), the increase width of CWND is one packet per ACK. , CWND> SSTHRESH (congestion avoidance state), the increase in CWND per ACK is 1 / CWND packet.

  On the other hand, when a packet loss is detected on the receiving side, the maximum sequence number + 1 (that is, the minimum value of the sequence number at which packet loss is detected) of continuously received packets is notified to the transmitting side by an ACK packet. If the sequence number (ACK number) in the ACK packet is duplicated on the receiving side (duplicate ACK), it is determined that the segment (one section of data) from the ACK number has been lost, and the lost segment is retransmitted. This is called high-speed retransmission.

  At this time, SSTHRESH = CWND / 2, and CWND = SSTHRESH + 3 * segment size. Each time another duplicate ACK arrives, CWND is incremented by the segment size, and a new packet is transmitted when transfer of a new packet is permitted by the value of CWND. When ACK for all the transmitted data is returned, CWND = SSTHRESH. The process up to this point after high-speed retransmission is called high-speed recovery. The throughput during high-speed recovery is less than half that before the loss. Thereafter, the congestion avoidance state is entered.

  Also, if the ACK does not return for a certain time, it is determined that the packet has been lost (timeout), the CWND is set to 1 packet, and the lost packet is retransmitted. Congestion control is described in Non-Patent Document 1.

  Further, for quick packet retransmission, a SACK (Selective ACK) option is defined as a TCP option (see, for example, Non-Patent Document 2). This option adds information to the ACK packet for notifying the transmission side from the reception side of the continuous period among the non-consecutive periods due to packet loss. The SACK option can notify a continuous section with a plurality of blocks at a time, and the latest reception sequence number is stored in the first block. For this reason, the transmitting side is notified of the maximum sequence number that has arrived at the receiving side (the maximum receiving sequence number on the receiving side).

  The transmitting side calculates a discontinuous section from the notified continuous sections and retransmits the segments of the discontinuous sections. The transmission side only needs to retransmit only the non-consecutive section, and the retransmission efficiency is good. Whether or not the non-consecutive section can be retransmitted can be determined by whether or not the ACK number exceeds the non-consecutive section. When the non-continuous section can be retransmitted, information on the continuous section before the non-continuous section is discarded.

  Even if this SACK option is used, the existing congestion control is the same as the conventional method described above, and when duplicate ACK is detected, the packet is retransmitted and CWND is halved. This SACK option is currently widely implemented and can be said to constitute part of the standard TCP.

  A problem with conventional TCP is that even for a single packet loss, the CWND is halved and the throughput is reduced, so if a random loss occurs, it cannot be used up even if the network bandwidth is free. is there. As a second problem, in a state where packet loss occurs frequently, the congestion avoiding state is not entered, and high-speed retransmission and high-speed recovery are repeated, resulting in an increase in throughput.

  In order to deal with the first problem of the conventional TCP described above, the reception side calculates the checksum of the received packet, and if the checksum does not match, notifies the transmission side that a random loss has occurred. There is a data transfer control method including a procedure of not performing flow control for congestion avoidance when a transmission side is notified that a random error has occurred (see, for example, Patent Document 1).

  In this method, it is necessary to change the TCP implementation on both the transmission side and the reception side. In a state where packet loss occurs frequently, the congestion avoiding state is not entered, and a state of repeatedly waiting for ACK for the retransmission of random packets occurs repeatedly, resulting in no throughput, and the conventional TCP first The problem of 2 is not solved.

  Furthermore, since this method retransmits a random loss packet and cannot send a new packet for 1 RTT until an ACK of the retransmitted packet is returned, the throughput decreases during this time. is there. With respect to this problem, fluctuations in the maximum ACK number and the maximum transmittable sequence number received on the transmission side will be described with reference to FIG.

  In order to simplify the explanation, it is assumed that the maximum transmittable sequence number is equal to the maximum ACK number on the receiving side + cwnd, and the buffer on the receiving side is sufficiently large. It is assumed that until the time A during the congestion avoidance state, the transmitting side has sent data up to the maximum transmittable sequence number to the receiving side.

  It is assumed that at time A, the transmission side detects that the packet with the sequence number x has randomly lost, and no other packets are lost. At this time, the transmission side retransmits the packet with the sequence number x and performs an operation without lowering cwnd. After this, since the ACK number transmitted from the transmission side does not advance (duplicate ACK) until time B (= time A + 1RTT) when the ACK corresponding to the retransmission packet is returned, the maximum transmittable sequence number is x + CWND remains unchanged.

  Therefore, in this section, the transmitting side cannot send a packet having a new sequence number to the receiving side. At time B, the sequence number of the ACK corresponding to the retransmission packet with the sequence number x is x + CWND, and the maximum transmittable sequence number is x + 2CWND. At this point, data for CWND can be transmitted and communication is performed in bursts. Is called.

  As another technique, there is a bandwidth control method including a procedure for maintaining CWND as it is without immediately reducing it at the time of packet loss detection and reducing CWND only when the subsequent packet loss situation deteriorates (for example, , See Patent Document 2).

  This method has a problem that if there is even one packet loss, a change in the number of losses is monitored while maintaining CWND, and the throughput does not increase. In a state where packet loss occurs frequently, the congestion avoiding state is not entered, and a state of waiting for an ACK corresponding to the retransmission of the lost packet occurs repeatedly, resulting in a loss of throughput. The problem of 2 is not solved.

  Further, this method has a problem that throughput is reduced during this time because a lost packet is retransmitted and a new packet cannot be transmitted for 1 RTT until an ACK of the retransmitted packet is returned. . With respect to this problem, fluctuations in the maximum ACK number and the maximum transmittable sequence number received on the transmission side will be described with reference to FIG.

  In order to simplify the explanation, it is assumed that the buffer on the receiving side is sufficiently large, and the maximum transmittable sequence number is equal to the maximum ACK number notified from the receiving side + CWND. It is assumed that until the time A during the congestion avoidance state, the transmitting side has sent data up to the maximum transmittable sequence number to the receiving side.

  Assume that at time A, the transmission side detects that the packet with the sequence number x is lost, and no other packets are lost. At this time, the transmission side retransmits the packet with the sequence number x and performs an operation without lowering CWND. After this, since the ACK number transmitted from the transmission side does not advance (duplicate ACK) until time B (= time A + 1RTT) when the ACK corresponding to the retransmission packet is returned, the maximum transmittable sequence number is x + CWND remains unchanged. Therefore, in this section, the transmitting side cannot send a packet having a new sequence number to the receiving side.

  At time B, the sequence number of the ACK corresponding to the retransmission packet of sequence number x is x + CWND, and the maximum transmittable sequence number is x + 2CWND. Is done.

Japanese Patent No. 3572111 Japanese Patent No. 3163479 W. By Richard Stevens, "TCP / IP Illustrated: The Protocols", Addison-Wesley, 1994. M.M. Mathis, J. et al. Mahdavi, S .; Floyd, A.M. Romanow, "RFC 2018-TCP Selective Acknowledgment Options", IETF, 1996.

  In the conventional congestion control technology described above, congestion is performed based on simple changes in the number of losses and explicit congestion information notified from the network. Although congestion control can be performed, the congestion control cannot be changed according to changes in a wider range of congestion conditions.

  Further, in the conventional congestion control technology, there is a problem that the throughput is reduced in a state where the loss rate is high because retransmission of the lost packet and subsequent recovery state occur repeatedly without entering the congestion avoidance state.

  Further, in the conventional congestion control technique, after the packet loss, the CWND on the receiving side and the maximum ACK number do not change and the maximum transmittable sequence number does not change, so the packet cannot be transmitted. There is a problem that throughput is reduced.

  Therefore, the object of the present invention is to solve the above-mentioned problems, and the loss rate is high only by changing the implementation of the transmission side terminal without changing the implementation of the reception side terminal or obtaining special information from the network. However, it is to provide a communication system, a communication apparatus, a congestion control method used for them, and a program thereof that can increase the throughput.

The communication system according to the present invention is a communication system using a window control method in which a receiving side designates a lost packet when recognizing a packet loss and requests retransmission to the transmitting side,
Estimating means for estimating the congestion state of the network from the information notified from the receiving side and one or more pieces of information on the congestion control state to the transmitting side, and overlapping according to the congestion state estimated by the estimating means. Means for distinguishing whether it is in a congestion state or not in the heavy congestion state, and means for retransmitting a lost packet while increasing a window for determining the transmission amount of the packet when it is not in the heavy congestion state. I have.

A communication apparatus according to the present invention is a communication apparatus that uses a window control system that designates a lost packet when the receiving side recognizes a packet loss and requests the transmitting side to retransmit,
Estimating means for estimating the congestion state of the network based on the information notified from the receiving side and one or more pieces of information on the state of congestion control to the processing means on the transmitting side, and the congestion state estimated by the estimating means Accordingly, the packet is retransmitted while increasing the window for determining the transmission amount of the packet when it is determined that it is not the heavy congestion state and the means for distinguishing whether it is the heavy congestion state or not. Means.

The congestion control method according to the present invention is a congestion control method used in a communication system that adopts a window control method for specifying a lost packet when a receiving side recognizes a packet loss and requesting a retransmission to the transmitting side.
The transmitting device estimates the network congestion state based on the information notified from the receiving side and one or more pieces of information on the congestion control state, and responds to the congestion state estimated by the estimating unit. For distinguishing whether the packet is in a heavy congestion state or not in the heavy congestion state, and for retransmitting a lost packet while increasing the window for determining the amount of packet transmission when it is determined that the packet is not in the heavy congestion state And running.

A program for a congestion control method according to the present invention is a program for a congestion control method used in a communication system that adopts a window control method for requesting retransmission to a transmission side by specifying a lost packet when the reception side recognizes packet loss,
An estimation process for estimating a network congestion state based on information notified from the reception side and one or more pieces of congestion control state to the computer performing the processing on the transmission side, and the congestion estimated by the estimation unit A process for distinguishing whether the state is a heavy congestion state or not a heavy congestion state according to the state, and a packet that is lost while increasing a window for determining the transmission amount of the packet when it is determined that the state is not the heavy congestion state And re-sending processing.

  That is, the first communication system of the present invention includes: a network state estimation unit that estimates a network congestion state using a packet loss state, packet arrival time information, and congestion control state; A light / heavy congestion determination unit that determines whether the status is light congestion or heavy congestion, a retransmission determination unit that determines whether to retransmit during light congestion or normal transfer, and retransmission during light congestion And a light congestion retransmission unit to perform.

  The first communication system of the present invention adopts the configuration as described above, and continuously increases the window even during light congestion, thereby obtaining changes in the implementation of the receiving terminal and special information from the network. Without changing the implementation of the transmitting terminal, the throughput can be increased even when the loss rate is high.

  In addition to the above configuration, the second communication system of the present invention has a maximum transmittable sequence number correction unit that increases and corrects the maximum transmittable sequence number in addition to the above configuration. The second communication system of the present invention adopts the above-described configuration, and prompts to transmit a new packet even during light congestion, thereby changing the receiving terminal implementation and special information from the network. It is possible to increase the throughput even when the loss rate is high only by changing the implementation of the transmitting terminal without obtaining the transmission rate, and it is possible to increase the throughput after resending the lost packet.

  The present invention is configured and operated as described above, so that the loss rate is high only by changing the implementation of the transmission side terminal without changing the implementation of the reception side terminal or obtaining special information from the network. Even in the state, an effect that the throughput can be increased is obtained.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a communication system according to an embodiment of the present invention. In FIG. 1, the communication system according to the embodiment of the present invention includes a transmission terminal 1, a reception terminal 2, and a communication network 100 for transmitting data from the transmission terminal 1 to the reception terminal 2.

  In the communication system according to the embodiment of the present invention, the transmission terminal 1 uses a packet loss state and packet arrival time information, and a congestion control state to estimate a network congestion state and a congestion state. A light / heavy congestion determination unit that determines whether the status is light congestion or heavy congestion, a retransmission determination unit that determines whether to retransmit during light congestion or normal transfer, and retransmission during light congestion A light congestion retransmission unit is provided.

  The communication system according to the embodiment of the present invention adopts the configuration as described above, and obtains special information from the network by changing the implementation of the receiving terminal 2 by continuously raising the window even during light congestion. Without changing, it is possible to increase the throughput even when the loss rate is high only by changing the implementation of the transmission terminal 1.

  In the communication system according to the embodiment of the present invention, in addition to the above configuration, the transmission terminal 1 is provided with a maximum transmittable sequence number correction unit that increases and corrects the maximum transmittable sequence number. The communication system according to the embodiment of the present invention adopts the above-described configuration, and prompts to transmit a new packet even during light congestion, thereby changing the implementation of the receiving terminal 2 or a special from the network. Without obtaining information, it is possible to increase the throughput even when the loss rate is high only by changing the implementation of the transmission terminal 1, and it is possible to increase the throughput after resending the lost packet.

  FIG. 2 is a block diagram showing the configuration of the session processing unit of the transmitting terminal according to the first embodiment of the present invention. 2, the session processing unit 10 includes a data input unit 11, a packet input unit 12, a congestion control unit 13, a data output unit 14, a packet output unit 15, a session state storage unit 16, and a segment buffer unit 17. It consists of and.

  The transmission terminal provided with the session processing unit 10 is the transmission terminal 1 of the communication system according to the embodiment of the present invention shown in FIG. 1 and receives the reception terminal 2 through the communication network 100 as in the embodiment of the present invention. Sending data to. In the transmission terminal 1, only the session processing unit 10 will be described in order to simplify the description. However, since processing units other than the session processing unit 10 are known, the description thereof will be omitted.

  The session processing unit 10 is a method of performing window-type congestion control using an acknowledgment (ACK: ACKnowledgement) packet. The session processing unit 10 describes only the part related to congestion control on the transmission side, session establishment / termination, data transmission / reception, ACK It is assumed that session data flows in one direction, omitting the description of the part related to transmission.

  The data input unit 11 inputs data from the terminal internal resource 3 that holds the data, and the packet input unit 12 inputs a packet from the communication network 100. The congestion control unit 13 processes signals from the data input unit 11 and the packet input unit 12. The data output unit 14 sends the data from the congestion control unit 13 to the terminal internal resource 3, and the packet output unit 15 sends the packet from the congestion control unit 13 to the communication network 100.

  The session state storage unit 16 holds information on the session processed by the congestion control unit 13, and the segment buffer unit 17 converts the data from the data input unit 11 to the data output unit 14 into segment delimiters that are data portions in the packet. Hold on.

  For the congestion control unit 13, a process related to an acknowledgment (ACK) packet process in the session process is described, and a description of a part related to a data transmission / reception process and a timer process is omitted.

  FIG. 3 is a block diagram showing a configuration of the congestion control unit 13 of FIG. In FIG. 3, the congestion control unit 13 includes a congestion determination unit 21, a network state estimation unit 22, a light / heavy congestion determination unit 23, a retransmission determination unit 24, a heavy congestion retransmission unit 25, and a light congestion retransmission unit 26. And a normal transfer unit 27 and a state update unit 28.

  The congestion determination unit 21 determines whether or not the current state is light / heavy congestion from the ACK packet and the stored contents of the session state storage unit 16, and if it is light / heavy congestion, the network state estimation unit 22 performs processing. Otherwise, it is determined that the normal state, and the process is transferred to the normal transfer unit 27. The network state estimation unit 22 estimates the network congestion state from the ACK packet and the stored contents of the session state storage unit 16.

  The light / heavy congestion determination unit 23 determines whether the congestion is light congestion or heavy congestion from the estimation result of the network state estimation unit 22, and if light congestion, the process is passed to the retransmission determination unit 24. Then, the process is passed to the heavy congestion retransmission unit 25. The retransmission determination unit 24 determines whether there is an unretransmitted segment that has not been retransmitted among the segments requested to be retransmitted by ACK from the reception side, and if there is an unretransmitted segment, passes the processing to the light congestion retransmission unit 26, If not, the process is transferred to the normal transfer unit 27.

  The heavy congestion retransmission unit 25 decreases the congestion window, searches the segment buffer unit 17 for a segment to be retransmitted, and passes the processing to the packet output unit 15 if there is a segment to be retransmitted. The light congestion retransmission unit 26 searches for a segment to be retransmitted from the segment of the segment buffer unit 17 by raising or maintaining the congestion window, or lowering the congestion window by the size of the segment of the retransmitted packet. If there is, the process is passed to the packet output unit 15.

  The normal transfer unit 27 raises the congestion window and passes the process to the packet output unit 15 if there is a new transmission segment in the segment buffer unit 17. The state update unit 28 updates the session state after the processes of the normal transfer unit 27, the light congestion retransmission unit 26, and the heavy congestion retransmission unit 25. Note that the retransmission determination unit 24 may retransmit a segment that has been retransmitted once, and there is no limit to the number of retransmissions.

  The re-transmission timing is when the new transmission sequence number is increased by x from the new sequence number when it is retransmitted or re-transmitted n times. The x number may be a plurality of values or a value calculated from the congestion window size. The best value for the x number is when the x number is the congestion window. This is because it is the smallest value among the effective values for the control interval of the window control method.

  Further, the re-transmission timing may be performed when time t elapses after retransmission or re-transmission n times. y may be a plurality of values. Also, t may be a value calculated from the delay time and the packet arrival interval. The best value is when y is the round trip delay time. This is because it is the smallest value among the effective values for the control interval of the window control method.

  The network state estimation unit 22 estimates the congestion state of the network using the information of the segment loss, the arrival time of the packet, and the state of the congestion control from the ACK packet and the stored contents of the session state storage unit 16. The segment loss information refers to segment loss location information recognized on the receiving side from the segment arriving on the receiving side. The packet time information indicates a packet arrival delay time and a packet arrival interval.

  As a method of estimating the network congestion state from the segment loss information, (a1) estimation based on variation in the arrival pattern of a new segment, (a2) estimation from the difference between the start sequence and end sequence of a segment non-continuous section, (a3 ) There are three estimations based on the amount of non-consecutive segments.

  In the estimation method of (a1), the network congestion state is estimated based on whether new segments arrive continuously at the receiving side or arrive non-continuously, and the new segments are non-continuous. It is estimated that the congestion is worse than when the new segments arrive continuously.

  In the estimation method (a2), when the difference between the start sequence and the end sequence of the segment discontinuous section increases, it is estimated that the congestion has deteriorated. The increase may be determined based on whether the sequence difference is x. x may be a fixed value or a value calculated from a congestion window. Further, in this estimation method, the sequence difference may be measured at regular intervals, and the network congestion state may be determined based on whether or not the value has increased.

  In the estimation method (a3), when the amount of non-consecutive segments increases, it is estimated that congestion has deteriorated. The amount of the segment non-continuous section is the amount of the segment non-continuous section grasped on the transmission side or the amount of the segment non-continuous section for each notification from the reception side. The increase may be determined based on whether or not the amount of the discontinuous section is x. x may be a fixed value or a value calculated from a congestion window. In this estimation method, the amount of non-consecutive sections may be measured at regular intervals, and the network congestion state may be determined based on whether the value has increased. Furthermore, in this estimation method, when the amount of non-consecutive sections per one increases, it may be estimated that congestion is getting worse.

  There are two methods for estimating the network congestion state from packet arrival time information: (b1) estimation based on how the packet arrival delay time increases, and (b2) estimation based on how the packet arrival interval increases.

  In the estimation method (b1), when the arrival delay time of the packet is increased, it is estimated that the congestion is deteriorated. Judgment of whether the arrival delay time tends to increase is determined by exceeding the threshold or taking an average value or deviation per unit time, and the average value and / or deviation exceeds or exceeds the threshold. If so, it is determined that the arrival delay time tends to increase. The best value for the arrival delay time is the round trip delay time. This is because the response confirmation packet can be used for easy measurement.

  In the estimation method (b2), when the packet arrival interval tends to increase, it is estimated that congestion has deteriorated. Judgment whether the arrival interval tends to increase has exceeded the threshold, or the average value and deviation per unit time are taken, and the average value and / or deviation have exceeded the threshold or increased. Then, it is determined that the arrival interval tends to increase.

  There are two methods for estimating the network congestion state from the congestion control state: (c1) estimation based on fluctuations in the number of re-transmissions, and (c2) estimation based on congestion duration.

  In the estimation method (c1), when the number of re-transmissions is increased, it is estimated that the congestion has deteriorated. The increase in the number of re-transmissions may be determined based on whether or not the number has reached x. x may be a fixed value or a value calculated from a congestion window. In this estimation method, the number of re-transmissions may be measured at regular intervals, and the network congestion state may be determined based on whether the value has increased.

  In the estimation method (c2), when the duration of congestion continues to increase, it is estimated that the congestion has deteriorated. The increase in the duration of congestion may be determined by determining whether the duration has reached time t. t may be a fixed value or a value calculated from the arrival delay time and the arrival interval. Further, in this estimation method, the network congestion state may be determined based on whether or not the current congestion duration time is increased as compared with the past congestion duration time.

  The network state estimation unit 22 may use any one or more of the above-described network congestion state estimation methods. The best estimation method is a method using all the estimation methods described above.

  FIG. 4 is a flowchart showing the operation of the congestion control unit 13 of FIG. The operation of the congestion control unit 13 according to the first embodiment of the present invention will be described with reference to FIGS.

  The ACK packet from the packet input unit 12 is supplied to the congestion determination unit 21. The congestion determination unit 21 determines whether the congestion state of the network is light / heavy congestion (step S1 in FIG. 4). If it is during heavy congestion, the process is transferred to the light / heavy congestion determination unit 23. Otherwise, the normal state is determined and the process is transferred to the normal packet transfer unit 27.

  The network state estimation unit 22 estimates the congestion state of the network from the ACK packet and the stored contents of the session state storage unit 16 (step S2 in FIG. 4). The light / heavy congestion determination unit 23 determines whether the current state is light congestion or heavy congestion from the estimation result of the network state estimation unit 22 (step S3 in FIG. 4). The process is passed to the determination unit 24, and if it is heavy congestion, the process is passed to the heavy congestion retransmission unit 25.

  The retransmission determination unit 24 determines whether there is an unretransmitted segment that has not been retransmitted among the segments requested to be retransmitted in the ACK packet from the receiving side (step S5 in FIG. 4). The process is passed to the light congestion retransmission unit 26, and if not, the process is passed to the normal transfer unit 27.

  The heavy congestion retransmission unit 25 reduces the congestion window, searches for a segment to be retransmitted from the segments in the segment buffer unit 17, and if there is a segment to be retransmitted, passes the processing to the packet output unit 15 (see FIG. 4 step S4).

  The light congestion retransmission unit 26 raises or maintains the congestion window, or lowers the congestion window by the size of the segment of the retransmission packet, and searches the segment of the segment buffer unit 17 for the segment to be retransmitted. If there is a segment, processing is passed to the packet output unit 15 (step S6 in FIG. 4).

  The normal transfer unit 27 raises the congestion window, and if there is a new transmission segment in the segment buffer unit 17, passes the processing to the packet output unit 15 (step S7 in FIG. 4). The state update unit 28 updates the session state after the processes of the normal transfer unit 27, the light congestion retransmission unit 26, and the heavy congestion retransmission unit 25 (step S8 in FIG. 4). Thereafter, the packet output unit 15 outputs the packet to the communication network 100 based on the processes of the normal transfer unit 27, the light congestion retransmission unit 26, and the heavy congestion retransmission unit 25 (step S9 in FIG. 4).

  In this embodiment, the congestion determination unit 21 and the light / heavy congestion determination unit 23 are provided separately. However, these determination units are integrated into one determination unit, and the normal state / light / heavy congestion determination is performed. It is good also as a part. Further, in this embodiment, the normal state / light congestion and heavy congestion may be divided into parts that determine normal and light congestion. That is, in the present embodiment, it is only necessary to determine three states as a result.

  In this embodiment, the light congestion retransmission unit 26 may continue the normal transfer unit 27 after the light congestion retransmission process. Furthermore, in this embodiment, the heavy congestion retransmission unit 25 may maintain a window. Furthermore, in this embodiment, the window may be increased with a lower increase rate than that of the normal transfer unit 27, and re-transmission may be performed as in the case of light congestion.

  Next, in the first embodiment of the present invention, a case will be described in which TCP (also referred to as Transmission Control Protocol or Transport Control Protocol) is used as a congestion control method.

  If the state held in the session state storage unit 16 is the normal state, the congestion determination unit 21 determines whether or not the passed ACK packet is a duplicate ACK and exceeds the threshold for the duplicate ACK. When the threshold value is exceeded, the state transits to a congestion state, and the process is passed to the light / heavy congestion determination unit 23.

  Further, if the state held in the session state storage unit 16 is a congestion state, the congestion determination unit 21 determines whether or not there is no sequence discontinuous section notified from the reception side by the SACK (Selective ACK) option.

  When there is no sequence discontinuous section, the congestion determination unit 21 determines that the normal state is reached, and passes the processing to the normal transfer unit 27. The congestion determination unit 21 passes the processing to the light / heavy congestion determination unit 23 when there is no sequence discontinuous section.

  As a method for determining whether or not there are no sequence discontinuous sections, the SACK information is no longer included in the ACK packet, or among the continuous sections of SACK held in the session state storage unit 16, the ACK sequence number greater than or equal to the ACK sequence number Judge by not having.

  The network state estimation unit 22 estimates the congestion state of the network from the stored contents of the ACK packet and the session state storage unit 16 using segment loss information, packet arrival time, and congestion control state information.

  As a method of estimating the network congestion state from the segment loss information, (d1) When the latest reception sequence number notified from the receiving side with the SACK option is duplicated and exceeds the threshold, the congestion is deteriorated. d2) When the difference between the maximum value of the transmitted sequence number (maximum transmission sequence number) and the ACK number in the sequence transmitted on the transmission side exceeds X × congestion window size, it is assumed that congestion deteriorates ( (X is an arbitrary value of 1 or more), (d3) When the difference between the latest reception sequence number notified from the reception side by the SACK option and the ACK number exceeds Y × congestion window size, congestion is (Y is an arbitrary value greater than 0) and (d4) a non-continuous section calculated from a continuous section notified from the receiving side by the SACK option If the amount in between exceeds Z × congestion window size, there are four, where congestion is exacerbated (Z is any value greater than 0 and less than 1).

  As a method for estimating a network congestion state from packet arrival time information, (e1) When the deviation of the round-trip delay time of a packet exceeds X × average value, it is assumed that the congestion deteriorates (X is from 0) (E2) (e2) When the deviation of the packet arrival interval exceeds Y × average value, it is assumed that congestion deteriorates (Y is an arbitrary value greater than 0). is there.

  As a method for estimating the network congestion state from the state of congestion control, (f1) When the number of re-transmissions exceeds X times, the congestion deteriorates (X is an integer value greater than 0). (F2) When the duration of congestion exceeds time Y × round trip delay time, there are two cases where congestion is worsened (Y is a value greater than 0).

  In the present embodiment, the network state estimation unit 22 may use any one or more of the above-described network congestion state estimation methods. The best way is to use everything.

  If the state held in the session state storage unit 16 is not heavy congestion, the light / heavy congestion determination unit 23 determines whether heavy congestion has occurred based on the estimation result of the network state estimation unit 22. When congestion occurs, the process is transferred to the heavy congestion retransmission unit 25. When congestion does not occur, the process is transferred to the retransmission determination unit 24. If the state held in the session state storage unit 16 is heavy congestion, the light / heavy congestion determination unit 23 determines whether or not heavy congestion continues based on the estimation result of the network state estimation unit 22. If heavy congestion continues, the process is transferred to the heavy congestion retransmission unit 25. If heavy congestion does not continue, the process is transferred to the retransmission determination unit 24.

  The retransmission determination unit 24 determines whether or not there is an unretransmitted segment that has not been retransmitted among the segments requested to be retransmitted by the reception side. If there is no unretransmitted segment, the process is transferred to the normal transfer unit 27.

  The transmitting side calculates the retransmission request section on the receiving side from the ACK sequence number and the SACK option. The sequence number of the ACK indicates the maximum sequence number received continuously, and the SACK option notifies the transmitting side of the continuous section among the sections that are discontinuous due to packet loss. From the above, it is possible to calculate the segment interval that is not received by the receiving side on the transmitting side.

  The light congestion retransmission unit 26 creates a packet to be retransmitted or retransmitted from the segments held in the segment buffer unit 17. At this time, the congestion window is not changed or decreased by the created segment size, the slow start threshold is not updated, and the flag indicating that normal retransmission is in progress is not set. That is, only the packet is retransmitted or retransmitted. The heavy congestion retransmission unit 25 performs high-speed retransmission and high-speed retransmission by halving the congestion window.

  FIG. 5 is a block diagram showing the configuration of the congestion control unit according to the second embodiment of the present invention. In FIG. 5, the congestion control unit 13a according to the second embodiment of the present invention is the same as the congestion control unit 13 according to the first embodiment of the present invention shown in FIG. The same components are denoted by the same reference numerals. The operation of the same component is the same as that of the first embodiment of the present invention. The communication system according to the second embodiment of the present invention has the same configuration as the communication system according to the embodiment of the present invention shown in FIG. 1, and the session processing unit according to the second embodiment of the present invention is shown in FIG. The same configuration as the session processing unit 10 according to the first embodiment of the present invention is shown.

  In the second embodiment of the present invention, the processing of the maximum transmittable sequence number correction unit 29 is executed before the processing of the normal transfer unit 27 after the retransmission determination unit 24 determines not to retransmit. The maximum transmittable sequence number correction unit 29 urges the normal transfer unit 27 to transmit a new packet even during light congestion by increasing and correcting the maximum transmittable sequence number. The corrected maximum transmittable sequence number is used for processing in the normal transfer unit 27 and is not held in the state update unit 28.

  FIG. 6 is a flowchart showing the operation of the congestion control unit 13a of FIG. The operation of the congestion control unit 13a according to the second embodiment of the present invention will be described with reference to FIG. 1, FIG. 2, FIG. 5, and FIG. Note that the processes in steps S11 to S16 and S18 to S20 in FIG. 6 are the same as the processes in steps S1 to S9 in FIG.

  When the retransmission determination unit 24 determines that there is no unretransmitted segment that has not been retransmitted among the segments requested to be retransmitted by the ACK packet by the retransmission determination unit 24 (step in FIG. 6). S15), the maximum transmittable sequence number is increased and corrected (step S17 in FIG. 6), and the process is transferred to the normal transfer unit 27.

  Next, a case where TCP is used as a session protocol in the second embodiment of the present invention will be described.

  As a method of correcting the maximum transmittable sequence number in the maximum transmittable sequence number correcting unit 29, the normal maximum transmittable sequence number is “maximum ACK sequence number notified from transmission + congestion window size”. Then, “maximum ACK sequence number + congestion window size + X” and arbitrary X are added for correction. X may be a positive fixed value or a value proportional to the congestion window.

  Further, in this embodiment, the maximum transmittable sequence number may be “the latest reception sequence number notified from the receiving side with the SACK option + congestion window size”.

  FIG. 7 is a block diagram showing the configuration of the congestion control unit according to the third embodiment of the present invention. In FIG. 7, the congestion control unit 13b according to the third embodiment of the present invention has the configuration of the congestion control unit 13 according to the first embodiment of the present invention shown in FIG. 3 except that the light congestion transfer unit 30 is provided. It has the same structure, and the same code | symbol is attached | subjected to the same component. The operation of the same component is the same as that of the first embodiment of the present invention. The communication system according to the third embodiment of the present invention has the same configuration as the communication system according to the embodiment of the present invention shown in FIG. 1, and the session processing unit according to the third embodiment of the present invention is shown in FIG. The same configuration as the session processing unit 10 according to the first embodiment of the present invention is shown.

  In the third embodiment of the present invention, when the retransmission determining unit 24 determines that there is no unretransmitted segment that has not been retransmitted among the segments requested to be retransmitted by ACK from the receiving side, the light congestion transfer unit Processing is passed to 30. The light congestion transfer unit 30 performs congestion control different from that of the normal transfer unit 27. The different congestion control refers to a control in which the increase width of the congestion window is lower than that of the normal transfer unit 27, or the congestion window is maintained for a while and then the congestion window is increased.

  FIG. 8 is a flowchart showing the operation of the congestion control unit 13b of FIG. The operation of the congestion control unit 13b according to the third embodiment of the present invention will be described with reference to FIG. 1, FIG. 2, FIG. 7, and FIG. Note that the processing in steps S21 to S26 and S28 to S30 in FIG. 8 is the same as the processing in steps S1 to S9 in FIG.

  When the light congestion transfer unit 30 determines that there is no unretransmitted segment that has not been retransmitted among the segments requested to be retransmitted in the ACK packet by the retransmission determination unit 24 (step S26 in FIG. 8). A transfer process for light congestion is performed (step S27 in FIG. 8).

  FIG. 9 is a block diagram showing the configuration of the congestion control unit according to the fourth embodiment of the present invention. In FIG. 9, the congestion control unit 13c according to the fourth embodiment of the present invention is the same as the congestion control unit 13b according to the third embodiment of the present invention shown in FIG. The same components are denoted by the same reference numerals. The operation of the same components is the same as that of the third embodiment of the present invention. The communication system according to the fourth embodiment of the present invention has the same configuration as the communication system according to the embodiment of the present invention shown in FIG. 1, and the session processing unit according to the fourth embodiment of the present invention is shown in FIG. The same configuration as the session processing unit 10 according to the first embodiment of the present invention is shown.

  In the fourth embodiment of the present invention, after the retransmission determining unit 24 determines that there is no unretransmitted segment that has not been retransmitted among the segments requested to be retransmitted by ACK from the receiving side, the light congestion transfer unit Before the process 30, the process of the maximum transmittable sequence number correction unit 29 is executed.

  The maximum transmittable sequence number correction unit 29 urges the light congestion transfer unit 30 to perform congestion control different from that of the normal transfer unit 27 during light congestion by increasing and correcting the maximum transmittable sequence number. The corrected maximum transmittable sequence number is used for processing in the light congestion transfer unit 30 and is not held in the state update unit 28.

  FIG. 10 is a flowchart showing the operation of the congestion control unit 13c of FIG. The operation of the congestion control unit 13c according to the fourth embodiment of the present invention will be described with reference to FIG. 1, FIG. 2, FIG. 9, and FIG. Note that the processes in steps S31 to S36 and S38 to S41 in FIG. 10 are the same as the processes in steps S21 to S30 in FIG.

  When the retransmission determination unit 24 determines that there is no unretransmitted segment that has not been retransmitted among the segments requested to be retransmitted by the ACK packet by the retransmission determination unit 24 (step in FIG. 10). S36), the maximum transmittable sequence number is increased and corrected (step S37 in FIG. 10), and the process is passed to the light congestion transfer unit 30. The light congestion transfer unit 30 performs transfer processing for light congestion (step S38 in FIG. 10).

  FIG. 11 is a block diagram showing a configuration of a transmission terminal according to the fifth embodiment of the present invention. In FIG. 11, the transmitting terminal according to the fifth embodiment of the present invention includes a packet input device 4, a packet output device 5, a data processing device 6, a storage device 7, and a congestion control program 8.

  The congestion control program 8 is read by the data processing device 6, controls the operation of the data processing device 6, generates a segment buffer 17 and a session state storage unit 16 in the storage device 7, exchanges data with the terminal internal resource 3, Packets are exchanged with the packet input device 4 and the packet output device 5.

  The data processor 6 controls the data input unit 11, the data output unit 14, the congestion control unit 13, the packet input unit 12, the packet output unit in the first to fourth embodiments of the present invention described above under the control of the congestion control program 8. The same processing as the processing by 15 is executed.

  As described above, the processing operation according to the first to fourth embodiments of the present invention described above is realized by the data processing device 6 performing the processing operation based on the control of the congestion control program 8.

  Although the present invention has been described with respect to the case where there are two types of congestion states in each of the above embodiments, there is no problem even if there are three or more types. That is, there is no problem even if light congestion is divided into two or more types. Moreover, there is no problem even if the heavy congestion is divided into two or more types.

  Moreover, although this invention has demonstrated the case where two terminals are used in each said Example, there is no restriction | limiting in the number of terminals. Furthermore, although the present invention has been described with respect to the case where the communication direction is one-way in each of the above-described embodiments, it may be bidirectional. Furthermore, the present invention describes the case where the transmitting terminal 1 and the receiving terminal 2 are separated from each other in each of the above embodiments. However, the functions of the transmitting terminal 1 and the receiving terminal 2 are the same in the terminal. It's okay. In this case, the transmission terminal 1 and the reception terminal 2 may each be a session repeater.

  Further, in the present invention, even if the cause of actual congestion is a random loss, the random loss is determined to be light congestion. Therefore, the present invention can achieve the object under such an environment.

  The present invention is applicable to terminal session communication, particularly TCP communication. The present invention can also be applied to the use of session relay devices such as proxies and encryption devices.

It is a block diagram which shows the structure of the communication system by embodiment of this invention. It is a block diagram which shows the structure of the session process part of the transmission terminal by 1st Example of this invention. It is a block diagram which shows the structure of the congestion control part of FIG. It is a flowchart which shows operation | movement of the congestion control part of FIG. It is a block diagram which shows the structure of the congestion control part by 2nd Example of this invention. It is a flowchart which shows operation | movement of the congestion control part of FIG. It is a block diagram which shows the structure of the congestion control part by the 3rd Example of this invention. It is a flowchart which shows operation | movement of the congestion control part of FIG. It is a block diagram which shows the structure of the congestion control part by the 4th Example of this invention. 10 is a flowchart illustrating an operation of a congestion control unit in FIG. 9. It is a block diagram which shows the structure of the transmission terminal by the 5th Example of this invention. FIG. 10 is a sequence diagram illustrating a throughput reduction problem during retransmission in Patent Document 1. FIG. 10 is a sequence diagram illustrating a throughput reduction problem during retransmission in Patent Document 2.

Explanation of symbols

1 Sending terminal
2 Receiving terminal
3 Terminal internal resources
4 Packet input device
5 Packet output device
6 Data processing device
7 Storage device
8 Congestion control program
10 Session processing section
11 Data input section
12 packet input unit 13, 13a,
13b, 13c Congestion control unit
14 Data output section
15 Packet output part
16 Session state storage
17 Segment buffer
21 Congestion judgment unit
22 Network state estimation unit
23 Light / Congestion Judgment Unit
24 Retransmission determination unit
25 Congestion retransmission unit
26 Light congestion retransmission part
27 Normal transfer section
28 State update section
29 Maximum transmittable sequence number correction section
30 Light Congestion Transfer Unit
100 communication network

Claims (58)

A communication system that uses a window control method that specifies a lost packet when the receiving side recognizes a packet loss and requests the sending side to retransmit,
Estimating means for estimating the congestion state of the network from the information notified from the receiving side and one or more pieces of information on the congestion control state to the transmitting side, and overlapping according to the congestion state estimated by the estimating means. Means for distinguishing whether it is in a congestion state or not in the heavy congestion state, and means for retransmitting a lost packet while increasing a window for determining the transmission amount of the packet when it is not in the heavy congestion state. A communication system comprising: The sender resends the packet,
The communication system according to claim 1, wherein the congestion control state used by the estimation unit to estimate a congestion state of the network is the number of retransmissions of the packet.   3. The communication system according to claim 1, wherein the congestion control state used by the estimation unit to estimate a congestion state of the network is a method of extending an arrival interval of the packet.   The communication according to any one of claims 1 to 3, wherein the information notified from the receiving side to the transmitting side is at least one of a segment loss point and an arrival time of the packet. system.   5. The communication system according to claim 4, wherein the estimation unit uses a variation of an arrival pattern of a new segment for estimating the congestion state of the network.   The communication system according to claim 4 or 5, wherein the estimation means uses a difference between a start sequence and an end sequence of a segment non-consecutive section for estimating the congestion state of the network.   The communication system according to any one of claims 4 to 6, wherein the estimation means uses an amount of a discontinuous section of a segment for estimating the congestion state of the network.   The communication system according to any one of claims 4 to 7, wherein the estimation unit uses a method of increasing an arrival delay time of the packet for estimating a congestion state of the network.   The communication system according to any one of claims 4 to 8, wherein the estimation unit uses a method of extending an arrival interval of the packets to estimate a congestion state of the network.   10. The means according to claim 1, further comprising means for retransmitting the lost packet while reducing the window when the transmitting side is identified as being in the heavy congestion state. 11. Communications system.   10. The means according to claim 1, further comprising means for retransmitting the lost packet while maintaining the window when the transmission side is identified as being in the heavy congestion state. Communications system.   2. The transmission side includes means for retransmitting the lost packet at a lower increment than when the window is not in a heavy congestion state when the transmission side is identified as being in the heavy congestion state. The communication system according to claim 9.   The transmission side includes a light congestion retransmission unit that retransmits a segment that has not been retransmitted among segments requested to be retransmitted while raising the window when it is identified as being in a light congestion state. The communication system according to any one of claims 1 to 12.   The transmission side includes a light congestion retransmission unit that retransmits a segment that has not been retransmitted among segments requested to be retransmitted while maintaining the window when the transmission side is identified as being in a light congestion state. The communication system according to any one of claims 1 to 12.   Light congestion retransmission means for retransmitting a non-retransmitted segment of the segments requested to be retransmitted by reducing the window corresponding to the segment size of the retransmission packet when the transmitting side is identified as being in a light congestion state The communication system according to claim 1, further comprising:   16. The maximum transmittable sequence number correcting means for increasing the maximum value of a sequence number that can be newly transmitted when the transmitting side is identified as being in a light congestion state. The communication system in any one.   The transmission side includes a maximum transmittable sequence number correction means that sets a maximum value of a sequence number that can be newly transmitted when it is discriminated to be in a light congestion state as “the maximum reception sequence number on the reception side + congestion window size”. The communication system according to any one of claims 1 to 15, characterized in that:   There is no normal transfer means for transmitting a new transmission packet while increasing the window when the network is not congested on the transmission side, and there is no unretransmitted segment that is not retransmitted among the segments requested to be retransmitted. 18. A light congestion transfer unit that transmits the new transmission packet while increasing the window at a lower width than the normal transfer unit when determined, and comprising: a light congestion transfer unit that transmits the new transmission packet. Communications system.   There is no normal transfer means for transmitting a new transmission packet while increasing the window when the network is not congested on the transmission side, and there is no unretransmitted segment that is not retransmitted among the segments requested to be retransmitted. The light congestion transfer means for transmitting the new transmission packet while increasing the window after maintaining the window for a predetermined time when it is determined. 18. Communications system. A communication device that uses a window control method that designates a lost packet when the receiving side recognizes packet loss and requests the sending side to retransmit,
Estimating means for estimating the congestion state of the network based on the information notified from the receiving side and one or more pieces of information on the state of congestion control to the processing means on the transmitting side, and the congestion state estimated by the estimating means Accordingly, the packet is retransmitted while increasing the window for determining the transmission amount of the packet when it is determined that it is not the heavy congestion state and the means for distinguishing whether it is the heavy congestion state or not. And a communication device. Resend the packet in the processing means on the transmission side,
21. The communication apparatus according to claim 20, wherein the congestion control state used by the estimating unit to estimate a congestion state of the network is the number of retransmissions of the packet.   The communication apparatus according to claim 20 or 21, wherein the congestion control state used by the estimation unit to estimate a congestion state of the network is a method of extending an arrival interval of the packet.   The information notified from the receiving side to the processing means on the transmitting side is at least one of a segment loss location and an arrival time of the packet. The communication apparatus as described in.   24. The communication apparatus according to claim 23, wherein the estimation unit uses a variation of an arrival pattern of a new segment for estimating the congestion state of the network.   25. The communication apparatus according to claim 23, wherein the estimation unit uses a difference between a start sequence and an end sequence of a segment non-consecutive section for estimating a congestion state of the network.   The communication apparatus according to any one of claims 23 to 25, wherein the estimation unit uses an amount of a non-continuous section of a segment for estimating a congestion state of the network.   27. The communication apparatus according to claim 23, wherein the estimation unit uses a method of increasing an arrival delay time of the packet for estimating a congestion state of the network.   28. The communication apparatus according to claim 23, wherein the estimation unit uses a method of increasing an arrival interval of the packet for estimating the congestion state of the network.   29. The method according to any one of claims 20 to 28, wherein the processing means on the transmission side includes means for retransmitting the lost packet while reducing the window when it is determined that the congestion state is present. The communication apparatus as described in.   29. The method according to claim 20, further comprising means for retransmitting the lost packet while maintaining the window when the processing means on the transmission side is identified as being in the heavy congestion state. The communication apparatus as described in.   The transmitting-side processing means includes means for retransmitting the lost packet with an increased width lower than that when the window is not in a heavy congestion state when it is distinguished from the heavy congestion state. The communication device according to any one of claims 20 to 28.   The transmission side processing means includes a light congestion retransmission means for retransmitting a non-retransmitted segment among the segments requested to be retransmitted while raising the window when it is determined that the state is light congestion. 32. The communication device according to any one of claims 20 to 31, wherein:   The transmission side processing means includes a light congestion retransmission means for retransmitting a non-retransmitted segment among the segments requested to be retransmitted while maintaining the window when it is determined that the state is a light congestion state. 32. The communication device according to any one of claims 20 to 31, wherein:   When it is determined that the processing means on the transmission side is in a light congestion state, a window corresponding to the segment size of the retransmission packet is reduced, and a non-retransmitted segment of the segments requested for retransmission is retransmitted. 32. The communication apparatus according to claim 20, further comprising a congestion retransmission unit.   21. The maximum transmission possible sequence number correction means for increasing the maximum value of a sequence number that can be newly transmitted when the processing means on the transmission side is identified as being in a light congestion state. Item 35. The communication device according to any one of item 34.   Maximum transmittable sequence number correction in which the maximum value of the sequence number that can be newly transmitted when it is determined that the processing means on the transmission side is in a light congestion state is “the maximum reception sequence number on the reception side + congestion window size” The communication apparatus according to any one of claims 20 to 34, further comprising: means.   A normal transfer means for transmitting a new transmission packet while increasing the window when the network is not in a congested state, and an unretransmitted segment that has not been retransmitted among the segments requested to be retransmitted. 37. A light congestion transfer means for transmitting the new transmission packet while increasing the window at a lower width than the normal transfer means when it is determined that there is no transmission, and comprising: The communication apparatus as described in.   A normal transfer means for transmitting a new transmission packet while increasing the window when the network is not in a congested state, and an unretransmitted segment that has not been retransmitted among the segments requested to be retransmitted. 37. A light congestion transfer means for transmitting the new transmission packet while increasing the window after maintaining the window for a predetermined time when it is determined that there is no transmission. 37. The communication apparatus as described in. A congestion control method used in a communication system that adopts a window control method in which a receiving side designates a lost packet when recognizing a packet loss and requests retransmission to the transmitting side,
The transmitting device estimates the network congestion state based on the information notified from the receiving side and one or more pieces of information on the congestion control state, and responds to the congestion state estimated by the estimating unit. For distinguishing whether the packet is in a heavy congestion state or not in the heavy congestion state, and for retransmitting a lost packet while increasing the window for determining the amount of packet transmission when it is determined that the packet is not in the heavy congestion state And a congestion control method. The sending device resends the packet;
40. The congestion control method according to claim 39, wherein the congestion control state used for estimating the congestion state of the network in the estimation process is the number of retransmissions of the packet.   41. The congestion control method according to claim 39 or 40, wherein the congestion control state used for estimating the congestion state of the network in the estimation process is a method of extending an arrival interval of the packet.   The information notified from the receiving side to the transmitting side device is at least one of a segment loss location and an arrival time of the packet. The congestion control method described.   43. The congestion control method according to claim 42, wherein a variation of an arrival pattern of a new segment is used to estimate a congestion state of the network in the estimation process.   44. The congestion control method according to claim 42 or 43, wherein a difference between a start sequence and an end sequence of segment discontinuous sections is used to estimate the congestion state of the network in the estimation process.   45. The congestion control method according to any one of claims 42 to 44, wherein an amount of non-consecutive segments is used to estimate a congestion state of the network in the estimation process.   46. The congestion control method according to claim 42, wherein a method of increasing an arrival delay time of the packet is used to estimate a congestion state of the network in the estimation process.   47. The congestion control method according to claim 42, wherein a method of increasing an arrival interval of the packet is used for estimating a congestion state of the network in the estimation process.   48. The method according to claim 39, wherein the transmitting apparatus executes a process of retransmitting the lost packet while reducing the window when it is determined that the apparatus is in the heavy congestion state. The congestion control method described in 1.   48. The process according to any one of claims 39 to 47, wherein the transmission side apparatus executes a process of retransmitting the lost packet while maintaining the window when it is determined that the apparatus is in the heavy congestion state. The congestion control method described in 1.   When the transmission side apparatus is identified as being in the heavy congestion state, it performs a process of retransmitting the lost packet with a lower increase width than in the case where the window is not in the heavy congestion state. The congestion control method according to any one of claims 39 to 47.   When the transmission side apparatus is identified as being in a light congestion state, it performs a light congestion retransmission process for retransmitting a segment that has not been retransmitted among the segments requested to be retransmitted while raising the window. 51. The congestion control method according to any one of claims 39 to 50, wherein:   When the transmission side apparatus is identified as being in a light congestion state, it performs a light congestion retransmission process that retransmits a segment that has not been retransmitted among segments requested to be retransmitted while maintaining the window. 51. The congestion control method according to any one of claims 39 to 50, wherein:   Light congestion for retransmitting non-retransmitted segments among the segments requested to be retransmitted by reducing the window corresponding to the segment size of the retransmitted packet when the transmitting device is identified as being in a light congestion state 51. The congestion control method according to claim 39, wherein retransmission processing is executed.   40. The maximum transmission possible sequence number correction process for increasing the maximum value of a sequence number that can be newly transmitted when the transmission side apparatus is identified as being in a light congestion state. 54. The congestion control method according to any one of items 53.   Maximum transmittable sequence number correction processing in which the maximum value of the sequence number that can be newly transmitted when the transmitting side apparatus is identified as being in a light congestion state is “the maximum receiving sequence number on the receiving side + congestion window size” 54. The congestion control method according to any one of claims 39 to 53, wherein:   A normal transfer process in which the transmission-side apparatus transmits a new transmission packet while increasing the window when the network is not congested, and an unretransmitted segment that is not retransmitted among the segments requested to be retransmitted. 56. The light congestion transfer process of transmitting the new transmission packet while increasing the window at a lower width than the normal transfer process when it is determined that there is no increase, and executing the light congestion transfer process. The congestion control method described in 1.   A normal transfer process in which the transmission-side apparatus transmits a new transmission packet while increasing the window when the network is not congested, and an unretransmitted segment that is not retransmitted among the segments requested to be retransmitted. 56. The light congestion transfer process of transmitting the new transmission packet while increasing the window after maintaining the window for a predetermined time when it is determined that there is no, and executing the light congestion transfer processing. The congestion control method described in 1. A program for a congestion control method used in a communication system that adopts a window control method in which a receiving side designates a lost packet when recognizing a packet loss and requests retransmission to the transmitting side,
An estimation process for estimating a network congestion state based on information notified from the reception side and one or more pieces of congestion control state to the computer performing the processing on the transmission side, and the congestion estimated by the estimation unit A process for distinguishing whether the state is a heavy congestion state or not a heavy congestion state according to the state, and a packet that is lost while increasing a window for determining the transmission amount of the packet when it is determined that the state is not the heavy congestion state A program for executing the resending process.

Images